Many electrical devices require a voltage above a certain point in order to operate effectively. Often these devices are powered by standard size batteries, e.g., AA, AAA, C, or D cell batteries, that output approximately 1.5V. With use, the output voltage of these batteries will decline below 1.5V. Thus, at some point the battery will no longer output a voltage sufficient to operate an electrical device. However, often the threshold voltage below which a device will no longer operate is still relatively high, e.g., a device may stop operating if the battery outputs less than 1.3V. This leaves a significant amount of energy still stored in the battery. Accordingly, there is a need to recover this remaining energy.